Kongsberg SBP 29, Installation Manual

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The signal is the echo that we want to know something about, while the noise is any
unwanted signals or disturbances. The echo must be detected in the noise and therefore
it is necessary to keep the noise level as low as possible in order to obtain high
interpretation.
The noise that contributes to the signal to noise ratio may be divided into the following
types of noise:
• Self noise
• Ambient noise
• Electrical noise
• Reverberation
A
The SBP 29 can pick up noise from
• Biological disturbances
• Interference
• Cavitation
• Propeller noise
• Flow noise
• Acoustic noise from other hydroacoustic systems
B
The SBP 29 cables are long, and may pick up electric noise from generators, pumps,
cooling systems and other electric or electromechanical devices.
C
The preamplifiers are very sensitive, and they can easily pick up electrical noise
from internal and external power supplies. The preamplifiers are also vulnerable to
analogue noise created by their own electronic circuitry. Digital noise created by
the converter and processing circuitry can also create problems.
D
Converters transform the analogue echoes to digital format.
E
Signal processing circuitry can create digital noise.
Self noise
Any vessel equipped with a hydroacoustic system (for example echo sounder or sonar)
will produce more or less self noise.
There are many sources of such self noise. We will here go into some details in order to
analyse the different sources of self noise on a vessel and how they may influence upon
the noise level of the hydroacoustic instruments.
Preparations